1. Field of the Invention
The present invention relates to a process liquid supply nozzle and a process liquid supply device for supplying a process liquid onto a substrate such as a semiconductor wafer and to a nozzle cleaning method, e.g., a process liquid supply nozzle and a process liquid supply device for supplying a coating liquid so as to form an interlayer insulating film on the surface of, for example, a semiconductor wafer and to a nozzle cleaning method.
2. Description of the Related Art
In the manufacturing process of a semiconductor device, an interlayer insulating film is formed on a semiconductor wafer by, for example, an SOD (Spin On Dielectric) system. In the SOD system, the wafer is coated with a prescribed coating liquid by the spin-coating method so as to form a coated film, followed by applying a physical treatment such as heating and a chemical treatment to the coated film so as to form an interlayer insulating film, as in the technology for coating the wafer with, for example, a resist solution.
In the case of forming an interlayer insulating film made of, for example, a siloxane-series polymer or an organic polymer, a wafer is disposed first on a spin chuck arranged within a cup. Then, while rotating the wafer, a coating liquid diluted with an organic solvent is discharged from a process liquid supply nozzle onto the center of rotation of the wafer so as to permit the coating liquid to be spread uniformly over the entire surface of the wafer, thereby forming a coated film. Further, the wafer is subjected stepwise to, for example, a heat treatment under the environment that is determined in accordance with the object of the heat treatment. Incidentally, depending on the kind of the coating liquid used, it is necessary to apply an additional treatment such as a treatment under an ammonia atmosphere or a chemical treatment such as a solvent replacing treatment after formation of the coated film.
The process liquid supply nozzle used in the particular spin-coating process comprises, for example, a discharge port formed in the lower portion for discharging the process liquid toward the surface of the wafer. Also, the upper portion of the nozzle is held by a moving mechanism. The process liquid supply nozzle is moved by the moving mechanism between the center of rotation of the wafer within the cup and a drain cup arranged outside the cup.
When the process liquid is supplied onto the wafer surface, the process liquid remains in the tip portion of the process liquid supply nozzle, and the remaining process liquid is condensed or solidified with time. If the condensed liquid or the solidified material thus formed is dropped onto the wafer surface during the supply of the coating liquid onto the wafer surface, the coating is rendered nonuniform or the coated film is rendered nonuniform in thickness.
For overcoming the above-noted problem, the present applicant proposed previously a process liquid supply nozzle and a process liquid supply device constructed as shown in FIGS. 14 and 15 in Japanese Patent Disclosure (Kokai) No. 2001-38272. FIG. 14 is a vertical cross sectional view schematically showing the constructions of the process liquid supply nozzle and the process liquid supply device, and FIG. 15 is a horizontal cross sectional view showing the construction of the holding member shown in FIG. 14.
As shown in FIG. 14, a process liquid supply nozzle 51 for discharging the process liquid so as to form an insulating film on the surface of a wafer is fixed to a nozzle holding member 50. The process liquid supply nozzle 51 comprises an outer pipe 52 having a large diameter and an inner pipe 54 having a small diameter and arranged inside the outer pipe 52. A holding member 60 for holding the inner pipe 54 within the outer pipe 52 is formed in the vicinity of a discharge port 53 of the outer pipe 52. The inner pipe 54 is held by the holding member 60 such that a discharge port 55 at the tip of the inner pipe 54 projects downward from the discharge port 53 formed in the tip of the outer pipe 52. Incidentally, the holding member 60 comprises a plurality of holes 60a as shown in FIG. 15 so as not to obstruct the downward flow of the cleaning liquid supplied into the outer pipe 52, as described herein later.
The coating liquid that is to be supplied onto the surface of the wafer is stored in a tank 56, and the coating liquid is supplied from within the tank 56 into the inner pipe 54 by a pump 57. Also, a cleaning liquid for cleaning the periphery of the tip portion of the inner pipe 54 is stored in a tank 58, and the cleaning liquid is supplied from within the tank 58 into the outer pipe 52 by a pump 59.
In the process liquid supply device of the construction described above, the coating liquid stored in the tank 56 is supplied into the inner pipe 54 by the pump 57, and further supplied onto the wafer surface through the discharge port 55. After completion of the coating operation, the nozzle holding member 50 is moved so as to permit the process liquid supply nozzle 51 to be moved to a position above a drain cup (not shown) and, then, the coating liquid remaining inside the inner pipe 54 is discharged into the drain cup. It should be noted that the remaining coating liquid is attached to the periphery in the tip portion of the inner pipe 54, particularly, to the outer circumferential surface in the tip portion of the inner pipe 54. Such being the situation, the cleaning liquid stored in the tank 58 is supplied into the outer pipe 52 by the pump 59 so as to allow the cleaning liquid to flow downward along the outer circumferential surface in the tip portion of the inner pipe 54, thereby washing away the coating liquid attached to the periphery in the tip portion of the inner pipe 54.
In the cleaning method of the process liquid supply nozzle 51 described above, however, the cleaning liquid flows downward along a part of the outer circumferential surface of the inner pipe 54. In other words, the particular cleaning method gives rise to the problem that the cleaning liquid fails to flow downward uniformly over the entire outer circumferential surface of the inner pipe 54. To be more specific, if the cleaning liquid is brought into contact with the outer circumferential surface of the inner pipe 54 so as to form a flowing streak of the cleaning liquid on the outer circumferential surface noted above, the cleaning liquid that is supplied subsequently flows along the flowing streak thus formed, failing to flow uniformly over the entire outer circumferential surface of the inner pipe 54. It follows that a portion that was not washed is formed on the outer circumferential surface of the inner pipe 54. Naturally, the coating liquid is left unremoved in the portion that was not washed.